For years I had problems growing Asclepias tuberosa. The germination was irregular and the few plants I got failed to thrive, sputtering along and then dying after a year or so. Even when I tried buying 3" pots they never did well for me. Most of the time if I fail with something a couple or three times I just give up - there are plenty of other things I can grow really well so why sweat the failures? I felt this way about butterfly weed until I saw one growing all by itself out in the middle of an empty lot on (of all places) Research Park Drive. It was the nicest butterfly weed I had ever seen, thriving among a bunch of weeds and grass and apparently unfazed about getting mowed over every 6 weeks. Surely it can't be that finicky if it grows well under those conditions! This was a few years ago and I decided to read up and figure out what I was doing wrong.
The germination problem partly stemmed from inconsistent directions. Some catalogs say to just plant the seed, no special directions. This is what I had tried before. Stokes Seeds , which usually provides detailed and accurate germination information, says to press the seeds into the soil without covering them, pre-chill the planted seeds at 34-40F for four weeks, and then warm them up to 65-70F and expose to light. On the other hand, Norman Deno, who is usually considered the final authority on how to start anything from seed, says to pre-chill but that the seeds do not require light and should be covered.
I ordered the seeds from GeoSeed and had planned on following Deno's directions but forgot to start them early enough to pre-chill. I figured the seed wouldn't be good the next year so I just planted them in a flat, and this time they came up like radishes! The seed source may have made the difference, maybe it was luck, I don't know.
When looking into the "failure to thrive" problem I found that Asclepias tuberosa is taprooted and does not transplant well. Alan Armitage writes in Specialty Cut Flowers, "If the taproot is broken the plant takes two years to recover - if it survives". Armitage suggests transplanting the seedlings into 4" pots by the time the second set of true leaves appear and then later gently moving them again into the field. I didn't have time or space to deal with 50 4" pots so instead I decided to plant the tiny seedlings directly into their final positions in the field. I had to fuss with them a bit, keeping an eye on the weeds and watering, but most of the little plants survived. The following year I was finally rewarded with a bed full of robust Asclepias tuberosa that bloomed profusely and even re-bloomed later in the summer. I liked them so well that I decided to start some more this year. I'm going to start some with the pre-chill method and some without and will report how it goes.